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Re: Response to Orenstein's "explanation" of mammal success.



In a message dated 96-06-10 15:54:23 EDT, jbois@umd5.umd.edu (John Bois)
writes:

>Ron uses snakes as an example and suggests that they could not be
>herbivores because of "early specialization" (for carnivory, I
>presume).

No, for narrowness.

>But this is silly.  Any snake worth the title has a long, thin body.
>Why?  So it can hide down holes.

Maybe initially (i.e. back in the Cretaceous), but, AFAIK, most snakes
today (at least the more visible types) do not live in holes.

>Why?  Because a selective pressure existed to make this a viable
>strategy to resist predation.  Having adapted for laying low,
>carnivory was the only option since herbivores must forage longer.

And, more to the point, require strong jaws and teeth and big guts, two
things very much in conflict with a snake's streamlining.

>Now, if you kill off everything else and make available a great
>range of niches, some of them _would_ evolve into herbivorous
>species.

Find me a snake that is even _capable_ of eating a plant and I'll
believe the above might be possible.

[...]

>Obligatory carnivory in snakes is strictly due to a lack of
>available niches.  Look also at the marine iguana of the Galapogos.
>It is a vegetarian among predominantly carnivores, lizards I mean.

Don't forget that the Galapagos land iguana is herbivorous, too.

> Yet it has adapted herbivorous structures.

Yes, FROM A VERY GENERALIZED IGUANA BODY FORM!!!  The situation here
is completely different from that in snakes.  Primitive iguanas had
strong teeth that could bite off plant matter, a long body that could
be adapted for plant fermentation, and no particular strictures on
body form.

Nick